Serpentine and corduroy circuits to enhance the stretchablity of a stretchable electronic device

ABSTRACT

A stretchable electronic apparatus and method of producing the apparatus. The apparatus has a central longitudinal axis and the apparatus is stretchable in a longitudinal direction generally aligned with the central longitudinal axis. The apparatus comprises a stretchable polymer body, and at least one circuit line operatively connected to the stretchable polymer body, the at least one circuit line extending in the longitudinal direction and having a longitudinal component that extends in the longitudinal direction and having an offset component that is at an angle to the longitudinal direction, the longitudinal component and the offset component allowing the apparatus to stretch in the longitudinal direction while maintaining the integrity of the at least one circuit line.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional PatentApplication No. 60/474,862 filed May 30, 2003 and titled “Serpentine andcorduroy designs to enhance the stretchablity of metalized silicone.”U.S. Provisional Patent Application No. 60/474,862 filed May 30, 2003and titled “Serpentine and corduroy designs to enhance the stretchablityof metalized silicone” is incorporated herein by this reference.

[0002] The United States Government has rights in this inventionpursuant to Contract No. W-7405-ENG-48 between the United StatesDepartment of Energy and the University of California for the operationof Lawrence Livermore National Laboratory.

BACKGROUND

[0003] 1. Field of Endeavor

[0004] The present invention relates to electronic devices and moreparticularly to a stretchable electronic device.

[0005] 2. State of Technology

[0006] U.S. Pat. No. 5,817,550 for a method for formation of thin filmtransistors on plastic substrates to Paul G. Carey, Patrick M. Smith,Thomas W. Sigmon, and Randy C. Aceves, issued Oct. 6, 1998, provides thefollowing state of technology information, “Recently a process wasdeveloped for crystallizing and doping amorphous silicon on a low cost,so-called low-temperature plastic substrate using a short pulsed highenergy source in a selected environment, without heat propagation andbuild-up in the substrate so as to enable use of plastic substratesincapable of withstanding sustained processing temperatures higher thanabout 180° C. Such a process is described and claimed in U.S. Pat. No.5,346,850 issued Sep. 13, 1994 to J. L. Kaschmitter et al., assigned tothe Assignee of the instant application. Also, recent efforts to utilizeless expensive and lower temperature substrates have been carried outwherein the devices were formed using conventional temperatures on asacrificial substrate and then transferred to another substrate, withthe sacrificial substrate thereafter removed. Such approaches aredescribed and claimed in U.S. Pat. Nos. 5,395,481 issued Mar. 7, 1995,No. 5,399,231 issued Mar. 21, 1995, and No. 5,414,276 issued May 9,1995, each issued to A. McCarthy and assigned to the assignee of theinstant application.”

[0007] U.S. Pat. No. 6,324,429 for a chronically implantable retinalprosthesis by Doug Shire, Joseph Rizzo, and John Wyatt, of theMassachusetts Eye and Ear Infirmary Massachusetts Institute ofTechnology issued November 27, 2001 provides the following state oftechnology information, “In the human eye, the ganglion cell layer ofthe retina becomes a monolayer at a distance of 2.5-2.75 mm from thefoveal center. Since the cells are no longer stacked in this outerregion, this is the preferred location for stimulation with anepiretinal electrode array. The feasibility of a visual prosthesisoperating on such a principle has been demonstrated by Humayun, et al.in an experiment in which the retinas of patients with retinitispigmentosa, age-related macular degeneration, or similar degenerativediseases of the eye were stimulated using bundles of insulated platinumwire.”

SUMMARY

[0008] Features and advantages of the present invention will becomeapparent from the following description. Applicants are providing thisdescription, which includes drawings and examples of specificembodiments, to give a broad representation of the invention. Variouschanges and modifications within the spirit and scope of the inventionwill become apparent to those skilled in the art from this descriptionand by practice of the invention. The scope of the invention is notintended to be limited to the particular forms disclosed and theinvention covers all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theclaims.

[0009] The present invention provides stretchable electronic apparatusand method of producing the apparatus. The apparatus has a centrallongitudinal axis and the apparatus is stretchable in a longitudinaldirection generally aligned with the central longitudinal axis. Theapparatus comprises a stretchable polymer body, and at least one circuitline operatively connected to the stretchable polymer body, the at leastone circuit line extending in the longitudinal direction and having alongitudinal component that extends in the longitudinal direction andhaving an offset component that is at an angle to the longitudinaldirection, the longitudinal component and the offset component allowingthe apparatus to stretch in the longitudinal direction while maintainingthe integrity of the at least one circuit line. In one embodiment thelongitudinal component that extends in the longitudinal direction andthe offset component that is at an angle to the longitudinal directioncomprise a 2-D serpentine circuit producing a spring in the at least onecircuit line. In another embodiment, the longitudinal component thatextends in the longitudinal direction and the offset component that isat an angle to the longitudinal direction comprise a 3-D corduroycircuit producing stress relieves structures in the at least one circuitline.

[0010] The apparatus has many uses. This includes use in shaped acousticsensors and transmitters; biological, chemical, temperature, andradiation sensors; sensors and stimulators for interfacing with humanbody and inanimate objects; non-destructive evaluation sensors; flexibledisplay monitors; smart notes; and monitoring devices. The apparatusalso has uses in implantable devices including epiretinal, subretinal,and cortical artificial vision implants, cochlear implants, neurologicalimplants, spinal cord implants and other neural interface implants;implantable and transdermal drug delivery devices; monitoring devices;implantable ribbon cables and electrode array for deep brainstimulation, spinal cord reattachment, nerve regeneration, corticalimplants, retinal implants, cochlear implants, drug delivery, musclestimulation and relaxation; and flexible displays and smart notes,conformable circuits as well as other uses.

[0011] The invention is susceptible to modifications and alternativeforms. Specific embodiments are shown by way of example. It is to beunderstood that the invention is not limited to the particular formsdisclosed. The invention covers all modifications, equivalents, andalternatives falling within the spirit and scope of the invention asdefined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are incorporated into andconstitute a part of the specification, illustrate specific embodimentsof the invention and, together with the general description of theinvention given above, and the detailed description of the specificembodiments, serve to explain the principles of the invention.

[0013]FIG. 1 illustrates an embodiment of a circuit constructed inaccordance with the present invention.

[0014]FIG. 2 is an enlarged view of a section of the circuit shown inFIG. 1.

[0015]FIG. 3 is a top view of another embodiment of a circuitconstructed in accordance with the present invention.

[0016]FIG. 4 is yet another embodiment of a circuit constructed inaccordance with the present invention.

[0017]FIG. 5 is a top view of the circuit shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring now to the drawings, to the following detaileddescription, and to incorporated materials, detailed information aboutthe invention is provided including the description of specificembodiments. The detailed description serves to explain the principlesof the invention. The invention is susceptible to modifications andalternative forms. The invention is not limited to the particular formsdisclosed. The invention covers all modifications, equivalents, andalternatives falling within the spirit and scope of the invention asdefined by the claims.

[0019] Referring now to in FIG. 1, an embodiment of an apparatusconstructed in accordance with the present invention is illustrated. Theapparatus is generally designated by the reference numeral 100. Theembodiment 100 provides a stretchable electronic circuit or electronicdevice 100. FIG. 1 also serves to illustrate an embodiment of theinvention that provides a polymer-based process to produce a circuit orelectronic device containing stretchable a conducting circuit.

[0020] The apparatus 100 has uses in shaped acoustic sensors andtransmitters; biological, chemical, temperature, and radiation sensors;sensors and stimulators for interfacing with human body and inanimateobjects; non-destructive evaluation sensors; flexible display monitors;smart notes; and monitoring devices. The apparatus 100 also has uses inimplantable devices including epiretinal, subretinal, and corticalartificial vision implants, cochlear implants, neurological implants,spinal cord implants and other neural interface implants; implantableand transdermal drug delivery devices; monitoring devices; implantableribbon cables and electrode array for deep brain stimulation, spinalcord reattachment, nerve regeneration, cortical implants, retinalimplants, cochlear implants, drug delivery, muscle stimulation andrelaxation; and flexible displays and smart notes, conformable circuitsas well as other uses.

[0021] The apparatus 100 comprises a stretchable electronic apparatushaving a central longitudinal axis. The apparatus 100 is stretchable ina longitudinal direction generally aligned with the central longitudinalaxis of the apparatus 100. The apparatus 100 utilizes a stretchablepolymer body 101 and at least one circuit line operatively connected tothe stretchable polymer body 101. Circuit lines 102A and 102B are shownfor illustrative purposes. As illustrated by FIG. 1, circuit lines 102Aand 102B extend in the longitudinal direction represented by thelongitudinal axes 103A and 103B. The longitudinal axes 103A and 103Bextend generally parallel to the longitudinal axis of the apparatus 100.Each circuit line 102A and 102B has a longitudinal component thatextends in the longitudinal direction and has an offset component thatis at an angle to the longitudinal direction. The longitudinal portionand the offset portion allow the apparatus 100 to stretch in thelongitudinal direction while maintaining the integrity of the circuitlines 102A and 102B.

[0022] Referring now to FIG. 2, an enlarged view of a portion of thecircuit line 102A of FIG. 1 is shown. The circuit line 102A extends in alongitudinal direction represented by the longitudinal axis 103A. Thelongitudinal axis 103A extends generally parallel to the longitudinalaxis of the apparatus 100. The circuit line 102A has a longitudinalcomponent 104A that extends in the longitudinal direction and has anoffset component 105A that is at an angle to the longitudinal direction.The longitudinal portion 104A and the offset portion 105A of the circuitline 102A allow the apparatus 100 to stretch in the longitudinaldirection while maintaining the integrity of the circuit lines 102A and102B.

[0023] The apparatus 100 uses dimethylsiloxane (PDMS) as the stretchablepolymer body 101. The stretchable polymer body 101 can be made in batchprocesses and provides a low-cost device that is ready for implantationwithout the need for additional packaging steps. The metal features arepatterned (deposited) on the stretchable polymer body 101. Thestretchable polymer body 101 is fabricated using PDMS which is an inertbiocompatible elastomeric material that has simultaneously low water andhigh oxygen permeability. The conformable nature of PDMS is useful forensuring uniform contact with the curved surfaces. PDMS is a form ofsilicone rubber, a material that is used in many implants and has beendemonstrated to withstand the body's chemical and physical conditionswithout causing adverse side effects, suggesting that PDMS may be afavorable material to implant within the body. Robustness of themetalized PDMS is another important design criterion because asstretching and bending occur during fabrication and implantation of thedevice 100.

[0024] The processes that can be used to produce thepoly-dimethylsiloxane (PDMS) stretchable polymer body 101 are describedin greater detail in United States Patent Applications Nos. 2003/0097165and 2003/0097166 and in the dissertation titled, “MICROFABRICATION OF ANIMPLANTABLE SILICONE MICROELECTRODE ARRAY FOR AN EPIRETINAL PROSTHESIS,”submitted in partial satisfaction of the requirements for the degree ofDoctor of Philosophy in Biomedical Engineering by one of the inventorsMariam N. Maghribi, University of California, Davis June 2003. Thedissertation formed part of U.S. Provisional Patent Application No.60/474,862 filed May 30, 2003 and priority of U.S. Provisional PatentApplication No. 60/474,862 filed May 30, 2003 is claimed in thisapplication. The disclosures of United States Patent Applications Nos.2003/0097165 and 2003/0097166 and the dissertation are incorporatedherein by reference.

[0025] Referring now to FIG. 3 another embodiment of an apparatusconstructed in accordance with the present invention is illustrated. Theapparatus is generally designated by the reference numeral 300. Theapparatus 300 provides a serpentine stretchable electronic circuit 302in an electronic device 300. FIG. 3 also serves to illustrate anembodiment of the invention that provides a polymer-based process toproduce an electronic device 300 containing serpentine stretchableconducting circuits illustrated by circuit 302. The process describedabove in connection with apparatus 100 can be used to produce theapparatus 300.

[0026] The apparatus 300 has many uses including the uses identifiedabove for the apparatus 100. One important use for the apparatus 300 isin implantable biomedical microdevice electrode and interconnectformation. Other uses include biocompatible interconnects for amultitude of surgical implants; implantable, biocompatible electricalinterconnect cabling; polymer based microelectrodes; polymer-basedmultilevel and multicomponent systems interconnect; applicationsrequiring flexible and stretchable electrical interconnect; fanoutmetalization for connectorization of integrated PDMS Microsystems;compact, hermetically sealed, high conductor density cabling; flexibleand stretchable electrically conducting interconnect for compactconsumer electronic products, internal and external medical deviceinterconnect; implantable devices; epiretinal, subretinal, and corticalartificial vision implant, cochlear implants, neurological implants,spinal cord implants and other neural interface implants; implantableand transdermal drug delivery devices; monitoring devices; implantableribbon cables and electrode array for deep brain stimulation, spinalcord reattachment, nerve regeneration, cortical implants, retinalimplants, cochlear implants, drug delivery, muscle stimulation andrelaxation; flexible displays and smart notes, conformable circuits; lowweight and profile high density conductors for aviation; and insulatedinterconnect cabling for aquatic applications such as environmentalmonitoring.

[0027] The serpentine circuits in the electronic apparatus 300 havecentral longitudinal axes illustrated by longitudinal axis 303 ofcircuit 302. The apparatus 300 is stretchable in a longitudinaldirection generally aligned with the central longitudinal axis of theapparatus 300. The apparatus 300 comprises a stretchable polymer body301 and the circuit lines operatively connected to the stretchablepolymer body 301. As illustrated by FIG. 3, the circuit lines extend inthe longitudinal direction as illustrated represented by thelongitudinal axis 303 of circuit 302. Each circuit line has alongitudinal component that extends in the longitudinal direction andhas an offset component that is at an angle to the longitudinaldirection. The longitudinal portion and the offset portion allow theapparatus 300 to stretch in the longitudinal direction while maintainingthe integrity of the circuit lines.

[0028] The view of the apparatus 300 shown in FIG. 3 is a top view. Theserpentine circuit 302 is a 2-D embodiment of a circuit incorporating aspring-like pattern to relive the stress in the thin film thereforeenhancing the stretchablity by increasing the percent strain of themetal traces 302 on the PDMS substrate body 301. The apparatus 300 canbe fabricated using traditional photolithographic patterning techniques.The serpentine circuit 302 has a longitudinal component that extends inthe longitudinal direction and has an offset component that is at anangle to the longitudinal direction. The longitudinal component thatextends in the longitudinal direction and the offset component that isat an angle to the longitudinal direction extend laterally from thelongitudinal axis 303 of the serpentine circuit 302.

[0029] Referring now to FIGS. 4 and 5, yet another embodiment of anapparatus constructed in accordance with the present invention isillustrated. The apparatus is generally designated by the referencenumeral 400. The embodiment 400 provides a corduroy stretchableelectronic circuit 402 in an electronic device 400. FIGS. 4 and 5 alsoserve to illustrate an embodiment of the invention that provides apolymer-based process to produce an electronic device 400 containing acorduroy stretchable conducting circuit 402. The process described abovein connection with apparatus 100 can be used to produce the apparatus400.

[0030] The apparatus 400 has uses in shaped acoustic sensors andtransmitters; biological, chemical, temperature, and radiation sensors;sensors and stimulators for interfacing with human body and inanimateobjects; non-destructive evaluation sensors; flexible display monitors;smart notes; and monitoring devices. The apparatus 100 also has uses inimplantable devices including epiretinal, subretinal, and corticalartificial vision implants, cochlear implants, neurological implants,spinal cord implants and other neural interface implants; implantableand transdermal drug delivery devices; monitoring devices; implantableribbon cables and electrode array for deep brain stimulation, spinalcord reattachment, nerve regeneration, cortical implants, retinalimplants, cochlear implants, drug delivery, muscle stimulation andrelaxation; and flexible displays and smart notes, conformable circuitsas well as other uses.

[0031] Referring now to FIG. 4, the apparatus 400 includes a corduroycircuit 402 with a central longitudinal axis 403. The centrallongitudinal axis 403 of the corduroy circuit 402 is generally parallelto the central longitudinal axis to the apparatus 400. The apparatus 400is stretchable in a longitudinal direction generally aligned with thecentral longitudinal axis of the apparatus 400 and the centrallongitudinal axis 403 of the corduroy circuit 402. The process describedabove in connection with apparatus 100 can be used to produce theapparatus 400.

[0032] Referring now to FIG. 5, a cross-sectional view of the apparatus400 is show. The apparatus 400 comprises a stretchable polymer body 401and a circuit line 402 operatively connected to the stretchable polymerbody 401. The circuit line 402 extends in the longitudinal direction andas illustrated by FIG. 5 the circuit line 402 extends in a verticaldirection above and below the longitudinal axis 403. The circuit line402 therefore has a longitudinal component that extends in alongitudinal direction and has an axial component that is at an angle tothe longitudinal direction. The longitudinal portion and the offsetportion allow the apparatus 400 to stretch in the longitudinal directionwhile maintaining the integrity of the circuit line 402. The serpentinecircuit 402 is a 3-D embodiment incorporating stress relievesstructures. In addition to photolithography, molding was required toachieve the 3-D rippled structure in the PDMS.

[0033] The apparatus 400 uses dimethylsiloxane (PDMS) as the stretchablepolymer body 401. The stretchable polymer body 401 can be made in batchprocesses and provides a low-cost device that is ready for implantationwithout the need for additional packaging steps. The metal features arepatterned (deposited) on the stretchable polymer body 401. Thestretchable polymer body 401 is fabricated using PDMS which is an inertbiocompatible elastomeric material that has simultaneously low water andhigh oxygen permeability. The conformable nature of PDMS is useful forensuring uniform contact with the curved surfaces. PDMS is a form ofsilicone rubber, a material that is used in many implants and has beendemonstrated to withstand the body's chemical and physical conditionswithout causing adverse side effects, suggesting that PDMS may be afavorable material to implant within the body. Robustness of themetalized PDMS is another important design criterion because asstretching and bending occur during fabrication and implantation of thedevice 400.

[0034] While the invention may be susceptible to various modificationsand alternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

The invention claimed is:
 1. A stretchable electronic apparatus, theapparatus having a central longitudinal axis and the apparatus beingstretchable in a longitudinal direction generally aligned with thecentral longitudinal axis, comprising: a stretchable polymer body, andat least one circuit line operatively connected to said stretchablepolymer body, said at least one circuit line extending in thelongitudinal direction and having a longitudinal component that extendsin the longitudinal direction and having an offset component that is atan angle to the longitudinal direction, said longitudinal component andsaid offset component allowing the apparatus to stretch in thelongitudinal direction while maintaining the integrity of said at leastone circuit line.
 2. The stretchable electronic apparatus of claim 1wherein said longitudinal component that extends in the longitudinaldirection and said offset component that is at an angle to thelongitudinal direction comprise a 2-D serpentine circuit producing aspring in said at least one circuit line.
 3. The stretchable electronicapparatus of claim 1 wherein said at least one circuit line has acircuit line longitudinal axis that extends generally parallel to thecentral longitudinal axis of the electronic apparatus and wherein saidlongitudinal component that extends in the longitudinal direction andsaid offset component that is at an angle to the longitudinal directionextend laterally from said circuit line longitudinal axis.
 4. Thestretchable electronic apparatus of claim 1 wherein said longitudinalcomponent that extends in the longitudinal direction and said offsetcomponent that is at an angle to the longitudinal direction comprise a3-D corduroy circuit producing stress relieves structures in said atleast one circuit line.
 5. The stretchable electronic apparatus of claim1 wherein said at least one circuit line has a circuit line longitudinalaxis that extends generally parallel to the central longitudinal axis ofthe electronic apparatus and wherein said longitudinal component thatextends in the longitudinal direction and said offset component that isat an angle to the longitudinal direction extend in a vertical directionabove and below said circuit line longitudinal axis.
 6. The stretchableelectronic apparatus of claim 1 wherein said stretchable polymer body issilicone.
 7. The stretchable electronic apparatus of claim 1 whereinsaid stretchable polymer body comprises poly(dimethylsiloxane).
 8. Thestretchable electronic apparatus of claim 1 wherein said at least onecircuit line comprises a conductive micron-scale wire.
 9. Thestretchable electronic apparatus of claim 1 wherein said at least onecircuit line comprises a conductive metal paste.
 10. The stretchableelectronic apparatus of claim 1 wherein said at least one circuit linecomprises a photolytic metal material.
 11. The stretchable electronicapparatus of claim 1 wherein said at least one circuit line comprises aconductive polymer.
 12. The stretchable electronic apparatus of claim 1wherein said stretchable polymer body comprises a microcable.
 13. Thestretchable electronic apparatus of claim 1 wherein said at least onecircuit line has a circuit line longitudinal axis that extends generallyparallel to the central longitudinal axis of the electronic apparatusand wherein said longitudinal component that extends in the longitudinaldirection and said offset component that is at an angle to thelongitudinal direction extend both laterally from said circuit linelongitudinal axis and vertically above and below said circuit linelongitudinal axis.
 14. The stretchable electronic apparatus of claim 1wherein said at least one circuit line has a circuit line longitudinalaxis that extends generally parallel to the central longitudinal axis ofthe electronic apparatus, said circuit line having a first section witha longitudinal component that extends in the longitudinal direction andan offset component that is at an angle to the longitudinal directionand extends laterally from said circuit line longitudinal axis, and asecond section with a longitudinal component that extends in thelongitudinal direction and an offset component that is at an angle tothe longitudinal direction and extends vertically above and below saidcircuit line longitudinal axis.
 15. A method of producing a stretchableelectronic apparatus having a central longitudinal axis and beingstretchable in a longitudinal direction generally aligned with thecentral longitudinal axis, comprising the steps of: providing astretchable polymer body; applying to said stretchable polymer body, acircuit line longitudinal component that extends in the longitudinaldirection, and applying to said stretchable polymer body, a circuit lineoffset component that is at an angle to the longitudinal direction, saidlongitudinal component and said offset component allowing the apparatusto stretch in the longitudinal direction while maintaining the integrityof said circuit line longitudinal component and said circuit line offsetcomponent.
 16. The method of claim 15 wherein said stretchable polymerbody is silicone.
 17. The method of claim 15 wherein said stretchablepolymer body comprises poly(dimethylsiloxane).
 18. The method of claim15 wherein said steps of applying to said stretchable polymer body acircuit line longitudinal component that extends in the longitudinaldirection and applying to said stretchable polymer body, a circuit lineoffset component that is at an angle to the longitudinal direction areapplied extending laterally from the central longitudinal axis.
 19. Themethod of claim 15 wherein said steps of applying to said stretchablepolymer body a circuit line longitudinal component that extends in thelongitudinal direction and applying to said stretchable polymer body, acircuit line offset component that is at an angle to the longitudinaldirection are applied extending vertically from the central longitudinalaxis.
 20. The method of claim 15 wherein said steps of applying to saidstretchable polymer body a circuit line longitudinal component thatextends in the longitudinal direction and applying to said stretchablepolymer body, a circuit line offset component that is at an angle to thelongitudinal direction are applied extending laterally and verticallyfrom the central longitudinal axis.
 21. The method of claim 15 whereinsaid step of applying to said stretchable polymer body a circuit lineoffset component that is at an angle to the longitudinal direction isapplied extending laterally and vertically from the central longitudinalaxis.
 22. The method of claim 15 including the steps of applying to saidstretchable polymer body a circuit line longitudinal component thatextends in the longitudinal direction and applying to said stretchablepolymer body, a circuit line offset component that is at an angle to thelongitudinal direction are applied extending laterally from the centrallongitudinal axis, and applying to said stretchable polymer body acircuit line longitudinal component that extends in the longitudinaldirection and applying to said stretchable polymer body, a circuit lineoffset component that is at an angle to the longitudinal direction areapplied extending vertically from the central longitudinal axis.